Nanoparticles, described in U.S. Pat. No. 5,145,684, are particles consisting of a poorly soluble therapeutic or diagnostic agent onto which are adsorbed a non-crosslinked surface modifier, and which have an average particle size of less than about 400 nanometers (nm).
As a result of their small size, lyophilization of therapeutic and diagnostic agents in nanoparticulate form stabilized by a surface modifier (surfactant) is difficult. Conventional lyophilization results in substantial growth of particle size, rendering the resulting particles unusable thus losing the desirable properties provided by rapid dissolution of small drug particles. The present invention describes the application of lyophilization to preparation of freeze-dried drug nanoparticles that retain their small particle size and can be readily redispersed.
This invention is directed to novel compositions that allow lyophilization of nanoparticles with reduced or no particle size growth. These compositions provide for an addition of cryoprotectants to nanoparticles such that the nanoparticles do not agglomerate during lyophilization. This invention is also directed to a method of making such compositions.